Download Third Head of Biceps Brachii Muscle, Associated with

Int. J. Morphol.,
32(2):510-514, 2014.
Third Head of Biceps Brachii Muscle, Associated with
Musculocutaneous and Median Nerve Bilateral Communication
and with a Communicating Branch Between Median Nerve Roots
Tercera Cabeza del Músculo Bíceps Braquial Asociada a la Comunicación Bilateral de los Nervios Musculocutáneo y Mediano y a un Ramo Comunicante entre las Raíces del Nervio Mediano
Aladino Cerda*,**
CERDA, A. Third head of biceps brachii muscle, associated with musculocutaneous and median nerve bilateral communication and with a
communicating branch between median nerve roots. Int. J. Morphol., 32(2):510-514, 2014.
SUMMARY: Both biceps brachii muscle anatomical variations and the presence of communicating branches between the
musculocutaneous nerve and the median nerve are common, and have clinical significance due to their connections and vulnerability. A case
found during a routine dissection of the upper limb of a male cadaver is described, in which unilateral presence of a third head of the biceps
brachii muscle coexists associated to a bilateral communication of the musculocutaneous nerve with the median nerve, and a unilateral
communicating branch between the roots of median nerve. The morphological features and the prevalence of the case are presented, besides the
discussion of its clinical significance.
KEY WORDS: Biceps brachii; Musculocutaneous nerve; Median nerve; Brachial plexus; Anatomical variations.
INTRODUCTION
The biceps brachii muscle has two heads, a short one
originated in the apex of the coracoids process, and a long
head originated in the supraglenoid tubercle of scapula (GarcíaPorrero & Hurlé, 2005). However, several articles in the
literature report supernumerary heads of the biceps brachii
muscle (Rodríguez-Niedenführ et al., 2003; Abu-Hijleh, 2005;
Vollala et al., 2008; Ilayperuma et al., 2011; Ongeti et al.,
2012). Some authors have described the coexistence of
communicating branches between musculocutaneous nerve
and median nerve associated to presence of an accessory humeral head of the biceps brachii muscle (Nayak et al., 2006;
Pacholczak & Klimek-Piotrowska, 2011; Ongeti et al.).
The musculocutaneous nerve, which is a branch of the
lateral cord of the brachial plexus, passes through the
coracobrachialis muscle to innervate it. Then it proceeds
between biceps brachii and brachial muscles giving branches
to innervate them, and continues as the lateral cutaneous nerve
of the forearm without any communication with the median
nerve, or other nerve (Sontakke et al., 2010). The median nerve
is constituted by a lateral and medial root; both originate from
lateral and medial cords of the brachial plexus, respectively.
Afterward, it traverses the lower portion of the axillary fossa,
descends through the arm and forearm, goes deep the flexor
*
**
retinaculum and finally reaches the hand palm, where it divides in its terminal branches.
The objective of this study was to describe the
topographic anatomy of these anatomical variations and
discuss its clinical implications.
CASE REPORT
During a routine dissection of the upper limbs of a
male cadaver, in the Morphology Laboratory of the Universidad de Talca, multiples anatomical variations were
observed. Axillary and brachial regions were carefully
dissected, and identified the constituent nerve roots of
brachial plexus, besides the route and distribution of its
terminal branches.
In the left upper limb (Fig. 1) a biceps brachii muscle
third humeral head was observed. That third head originated
at the humeral medial face, at level of third middle of arm,
between coracobrachialis muscle insertion and brachialis
muscle origin. It was 14.9 cm length and was joined to the
Unidad de Anatomía, Departamento de Ciencias Básicas Biomédicas, Facultad de Ciencias de la Salud, Universidad de Talca, Talca, Chile.
Programa de Magíster en Ciencias, mención Morfología, Facultad de Ciencias de la Salud, Universidad de la Frontera, Temuco, Chile.
510
CERDA, A. Third head of biceps brachii muscle, associated with musculocutaneous and median nerve bilateral communication and with a communicating branch between median nerve roots.
Int. J. Morphol., 32(2):510-514, 2014.
Fig. 1. Anterior view of left arm. MaP: major pectoral muscle; CB:
coracobrachialis muscle; MCN: musculocutaneous nerve; LH: long
head of the biceps brachii muscle; SH: short head of the biceps brachii
muscle; B: brachialis muscle; *: third head of the biceps brachii
muscle; MB: muscularbranch; LCFN: lateral cutaneous forearm
nerve; C: communicating branch; MN: median nerve.
Fig. 3. Anterior view of right axilla. MaP: major pectoral muscle;
CB: coracobrachialis muscle; MCN: musculocutaneous nerve; LH:
long head of the biceps brachii muscle; SH: short head of the biceps
brachii muscle; B: brachialis muscle; LR: lateral root of the median
nerve; MR: medial root of the median nerve; C: communicating
branch; AA: axilary artery; MN: median nerve.
biceps brachii tendon at level of third lower of arm. In this limb, we also observed
the presence of a communicating branch between musculocutaneous and median
nerve. In this case the musculocutaneous nerve penetrated the coracobrachialis
muscle and gave three terminal branches at level of third lower of arm; a muscular
branch to innervate the brachial muscle, the lateral cutaneous forearm nerve, and
a communicating branch that originated 19.1 cm away from the apex of the coracoid
process with a 7.7 cm length and a 1.6 mm thickness, and finally it connected to
median nerve to 25.9 cm away from the coracoid process.
In the right upper limb (Fig. 2) the musculocutaneous nerve penetrated the
coracobrachialis muscle and gave four terminal branches at level of third lower of
arm; two muscular branches for the brachial muscle, the lateral cutaneous forearm
nerve and a communicating branch. The last one originated 18.4 cm away from
the apex of the coracoid process; next it descends to medial with a 9.4 cm length
and 1.2 mm thickness, and finally connects to median nerve 28.7 cm away from
the apex of coracoid process. The presence of a little communicating branch that
originated from the medial root of the median nerve was also observed, descended
obliquely to lateral, crossing anterior of axillary artery and finally connecting to
the lateral root of median nerve, at 0.4 cm away from its origin; presented a 2.1 cm
length and 1 mm thickness (Fig. 3).
Fig. 2. Anterior view of right arm. MaP: major pectoral muscle; CB: coracobrachialis
muscle; MCN: musculocutaneous nerve; LH: long head of the biceps brachii muscle; SH:
short head of the biceps brachii muscle; B: brachialis muscle; 1 and 2: muscular branches;
C: communicating branch; LCFN: lateral cutaneous forearm nerve; MN: median nerve.
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CERDA, A. Third head of biceps brachii muscle, associated with musculocutaneous and median nerve bilateral communication and with a communicating branch between median nerve roots.
Int. J. Morphol., 32(2):510-514, 2014.
DISCUSSION
The presence of the supernumerary heads of the
biceps brachii muscle has been associated with variations
of the musculocutaneous nerve; likewise, it has been
associated with the presence of communicating branches,
between the median nerve and musculocutaneous nerve
(Rodríguez-Niedenführ et al.; Abu-Hijleh; Pacholczak &
Klimek-Piotrowska). The embryological development of the
upper limbs may help in explaining this anatomical variation.
The mesenchyme, which forms the upper limb muscles, is
penetrated by the ventral primary branches of the appropriate
spinal nerves, located opposite to the bud. Contact between
nerves and muscle cells, is necessary to provide
mesenchymal condensation to form muscles. Nerves
supplying the limbs are joined by loops connection of nerve
fibers to form plexuses. The median nerve is formed by a
combination of ventral segmental branches and the
musculocutaneous nerve arises from it (Pacholczak &
Klimek-Piotrowska). The development of the biceps brachii
third humeral head may have influenced the course or the
ramification patterning of variant musculocutaneous nerve,
or vice versa, and could explain the coexistence of such
neuromuscular anomaly (Abu-Hijleh).
The presence of a third humeral head is the most
common anatomical variation of biceps brachii muscle
(Rodríguez-Niedenführ et al.) and has been frequently
reported (Rodríguez-Niedenführ et al.; Abu-Hijleh; Vollala
et al.; Ilayperuma et al.; Ongeti et al.). The presence of four
or even seven biceps brachii muscle heads has also been
reported (Catli et al., 2012). The available combinations of
these variations have resulted in a large number of reports
and studies, with different classification systems, making
comparison difficult (Rodríguez-Niedenführ et al.).
Rodríguez-Niedenführ et al., classifies the
supernumerary heads of biceps brachii muscle according its
location, as a superior humeral head, inferomedial and
inferolateral. The superior humeral head, presents a proximal
attachment in the surface of the humerus, between the lesser
tubercle, the brachial and coracobrachial muscles. Then it
continues inferiorly, deep to the short head of biceps brachii
muscle and superficial to the anterior humeral circumflex
artery, and merges with muscle fibers of the short head of
biceps brachii muscle in its join with the long head. The
inferomedial head has a proximal attachment in the
anteromedial surface of humerus, continues with the insertion
of coracobrachialis muscle and closely related to the medial
intermuscular septum and brachial muscle; then continues
inferiorly, deep to the biceps brachii muscle and superficial
to the brachial muscle, inserting in the medial border of the
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biceps brachii tendon. The inferolateral head originates in
the lateral intermuscular septum, between the insertion of
the deltoid and the origin of the brachioradialis muscle, and
joins to the long head of the biceps brachii muscle at the
level of lower third of arm. According to this classification,
the third head of biceps brachii muscle found in this case
corresponds to an inferomedial humeral head. According
Rodríguez-Niedenführ et al. this is the most common
variation (9%).
Anatomical variations and anomalies of the upper
extremity muscles are significant, because doctors can find
such abnormalities during image forming with computed
tomography and magnetic resonance imaging (Catli et al.).
Magnetic resonance imaging and computed tomography play
an important role in distinguishing between normal
anatomical structures and pathological lesions of the upper
extremity, as well as serving as a guide for planning surgical
resection. Therefore, the presence of an accessory head can
lead to confusion (Kervancioglu & Orhan, 2011). In most
cases, the accessory heads are asymptomatic and represent
incidental findings encountered during surgery or images
(Kervancioglu & Orhan). From a clinical standpoint, muscle
anomalies are difficult to differentiate from soft tissue tumors
(Nayak et al., 2008). The existence of accessory muscles in
the arm and forearm may confuse surgeons during
procedures, cause compression of the neurovascular
structures, or lead to the variation of the normal mechanical
action (Lee et al., 2011). If the variation is unilateral, this
can be the cause of the mismatch between the two arms,
which can be easily confused with pathological conditions
such as tumors (Kervancioglu & Orhan).
An accessory head of biceps brachii could cause an
additional force or an unusual displacement of the fragments
of the humerus after fracture (Mas et al., 2006). According
Balasubramanian (2010), this third head of the biceps brachii
would allow flexion of the elbow joint, irrespective of the
position of the shoulder joint. Ongeti et al. add that these
unusual muscles also enhance supination.
The presence of communicating branches between
the musculocutaneous nerve and median nerve are common,
and has been reported by several authors (Venieratos &
Anagnostopolou, 1998; Choi et al., 202; Loukas & Aqueelah,
2005; Anyanwu et al., 2009; Cerda & Suazo, 2012). The
most frequent variation consists in the presence of a
communicating branch, originated from the
musculocutaneous nerve and joins distally to the median
nerve, at level of lower third of arm (Venieratos &
Anagnostopoulou). Such variations are predominantly unilateral (Saeed & Rufai, 2003). According Choi et al. the bilateral variations are very rare.
CERDA, A. Third head of biceps brachii muscle, associated with musculocutaneous and median nerve bilateral communication and with a communicating branch between median nerve roots.
Int. J. Morphol., 32(2):510-514, 2014.
The communication between the musculocutaneous
nerve and median nerve has been classified by many authors,
based on different criteria (Cerda & Suazo). Venieratos and
Anagnostopoulou classified communications between the
median nerve and musculocutaneous nerve into three types,
according its relationship with coracobrachialis muscle. In
the types I and II communications are proximal and distal at
the entry point of the musculocutaneous nerve in the
coracobrachialis muscle, respectively. In the type III the
musculocutaneous nerve, as well as the communicating
branch, do not penetrate coracobrachialis muscle. According
to this classification the communicating branches between
the musculocutaneous nerve and median nerve found in this
case correspond to type II, in both upper limbs. . In six
subjects of the study by Venieratos & Anagnostopoulou these
communications were bilateral. Within the six subjects, one
presented a pattern type II bilateral (1.3%; 1 of 79 cadavers),
the same as found in this case.
Choi et al. classified the communicating branch
between the musculocutaneous nerve and median nerve in
three patterns, based on the communicating branch numbers
or the fusion of both nerves. In the pattern I the
musculocutaneous nerve and median nerve merge forming
a trunk. In pattern II and III two and three communicating
branches between musculocutaneous nerve and median
nerve were present, respectively. According to this
description, the findings in this case may be classified as a
pattern II in both upper limbs. Loukas & Aqueelah classified
the communications between the musculocutaneous nerve
and median nerve in four models, according to its relationship
with coracobrachialis muscle. In type I and II the
communications are proximal and distal to the entry point
of the musculocutaneous nerve in the coracobrachial muscle,
respectively; meanwhile, in the type III the
musculocutaneous nerve does not penetrate the
coracobrachialis muscle, and in type IV both types I and II
coexist. According to this classification, the findings in this
report correspond to a pattern type II, in both upper limbs.
Clinically, these variations may be related to
entrapment syndrome. If the entrapment of the
musculocutaneous nerve coexists with a communicating
branch between the musculocutaneous and median nerve
may lead symptoms of median nerve neuropathy (Goyal et
al., 2005). This knowledge may result useful to doctors to
avoid an unnecessary carpal tunnel release (Venieratos &
Anagnostopoulou).
The communicating branch between the roots of the
median nerve has been reported previously by Badawoud
(2003). He described the presence of two communicating
branches between roots of median nerve. Both ranged from
the medial root to the lateral root of the nerve, and likewise
in this case, the presence was unilateral with a 2.1%
frequency (1 of 48 upper limbs)
According Singhal et al. (2007) the anomalous
communicating branches that crosses the axillary artery by
its anterior view, can cause compression syndromes,
producing ischemia. According to Badawoud, the presence
of this communicating branch could compress the axillary
artery and reduce blood supply to the upper limb.
Due to the frequency with which diagnostic and
surgical procedures are performed at the upper limbs, the
knowledge of such anatomical variations is important in order
to avoid errors in the diagnosis or undesirable consequences.
CERDA, A. Tercera cabeza del músculo bíceps braquial asociada a la comunicación bilateral de los nervios musculocutáneo y mediano y
a un ramo comunicante entre las raíces del nervio mediano. Reporte de un caso. Int. J. Morphol., 32(2):510-514, 2014.
RESUMEN: Tanto las variaciones anatómicas del músculo bíceps braquial como la presencia de ramos comunicantes entre los
nervios musculocutáneo y mediano son frecuentes y tienen importancia clínica, debido a sus relaciones y vulnerabilidad. Se describe un
caso encontrado durante una rutina de disección de los miembros superiores de un cadáver masculino, en el que coexiste la presencia
unilateral de una tercera cabeza del músculo bíceps braquial asociada a una comunicación bilateral entre los nervios musculocutáneo y
mediano junto a un ramo comunicante unilateral entre las raíces del nervio mediano. Se presentan sus características morfológicas, su
prevalencia y se discute su importancia clínica.
PALABRAS CLAVE: Bíceps braquial; Nervio musculocutáneo; Nervio mediano; Plexo braquial; Variaciones anatómicas.
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Correspondence to:
Aladino Cerda Alarcón
Universidad de Talca
Departamento de Ciencias Básicas Biomédicas
Avenida Lircay s/n Oficina N° 1, Talca
CHILE
E-mail: [email protected]
Received: 10-01-2014
Accepted: 14-04-2014